Reservoir for hydraulic system



Oct. 3, 1961 R. F. BRAcKlN REsERvoIR FOR HYDRAULIC SYSTEM Filed Feb. 4, 1958 v/ E R. w mm NO w MA .M R .l F. D M I. W K

f* 3,@@,355 H Fatented Oct. 3,` 1961 I 3,002,`355 RESERVOIR FOR HYDRAULIC SYSTEM Richard F. Brackiu, 'Drexel Hill, Pa., assignor to The Yale and Towne Manufacturing Company, Starnford, Conn., a corporation of Connecticut 'Filed Feb. 4, 1958, Ser. No. 713,199 3 Claims. (Cl. 60-52) This invention relates to a tank functioning as the reservoir for a hydraulic system, and more particularly, that form of 'hydraulic system found in load lifting assemblies, as for example, industrial trucks.

In truck assemblies of the class described, it is customary to utilize a tank containing fiuid adapted for useV with hydraulic rams, a pump being employed for forcing the flud under pressure into one or more rams for actuating the rams. When the rams are not operated, the fiuid must naturally be by-passed, particularly where the pump is continuously operated during the running of the truck motor, as is the case in most industrial trucks. It is obvious that with the pump moving the fiuid and the fiuid by-passing the ram or rams, there is very co-nsiderable turbulence contributed to the flud within the reservoir. This is particularly true where the motor of the truck is Operating at a fairly high speed. With the fiuid in a state of high turbulence, should the operator wish to direct the fiuid to the rams for Operating the rams, it is obvious that the fluid moving toward the rams will not be in a desirable condition due to cavitation and excessive aeration, The same condition will arise When an attempt is made to operate the rams at high speed through the running of the truck motor at a relatively high s eed.

To obviate the difficulties that I have discussed, it has become customary to place a bafle in the hydraulic fiuid tank, the bafile being lmounted in a Vertical position and so formed that fiuid being by-passed or moving from the rams enters the tank at 'one side of the bafiie, the flud moving to the pump and rams being taken from the' other side of the bafiie. This allows the flud while moving from one side of the bafile to the other to settle, to'lose its air bubbles and reduce its turbulence prior to movement toward the rams. When the motor operates at very high speed, the fiuid moving toward the rams will be rapidly taken from the tank at one side of the baflie and frequently, the level there will drop so swiftly that there Will not be adequate fiuid available, the baffie preventing sufiiciently swift flow under the circumstances described. Therefore, while the baffle is somewhat effective under some crcumstances, it will actually, under other circumstances, prevent the proper operation of the hydraulic system.

I have now conceived a tank construction that functions very eifectively in a hydraulic lifting system of the class described. Basically, I provide substantially a closed passage from the inlet pipe of the tank to that pipe leading to the pump and rams. This means that the pipe coming into the tank from the by-pass valve, or from the rams, it in almost direct communication with the pipe leading from the tank to the pump and the rams. To permit cooling of the fiuid moving in by-pass relation to therams or from the rams, I provide means whereby there is actually some interchange between the fiuid in the tank and the fiuid fiowng through the subistantially closed passage I have just described. The interchange, moreover, permits flow of fiuid from the substantially closed passage during the by-passing of the rams. In other words, fiuid Will flow from the tank to the pump and thence to the rams or in by-pass relation to the rams. The fiuid will then move back to the tank and in the tank will flow through the substantially closed passage toward the pipe leading to the pump. There will be sufiicient flud interchange in the tank for cooling of the fiuid, and any possible excess of flud flowing 'm the pipe coming into the tank will move into the tank.

More particularly, my invention utilizes a relatively enlarged passage within the tank, one end of which is in communication with the inlet pipe leading from the bypass or rams. The other end of this enlarged passage is in communication with the pipe leading to the pump and then to the rams, or in'the alternative, the pump and the by-pass valve. The enlarged passage has openings through which communication may be had with the tank so that there can be some interchange between the fluid in the enlarged passage and the fiuid in the tank. Oibviously, therefore, there will be a flow of fluid into the enlarged passage, an interchange of fiuid and a further flow toward the pump. This effects a simple practically continuous passage of fiuid to the pump from the tank and back into the tank once again, with provision for ample fiuid interchange to effect cooling and to. Permit acceptance of surges in fiuid flow in one or the other direction;

I have thus outlined rather broadly the more important features of my invention in order that the detailed description thereof that follows may be better understood, and in order that my contribution to the art may be better appreciated. There are, of course, additional features of my invention that will be described hereinafter and which will form the subject of the claims appended hereto. Those skilled in the art will appreciate that theoconcep- Vtion on which my disclosure is based may readily be utilized ,as a basis for the designing of other structures for carrying out the several purposes of my invention. It is important, therefore, that the claims be regarded as including such equivalent constructions as do not depart 'from the spirit and scope of my invention, in order to prevent the appropriation of my invention by those skilled in the art.

An illustrative embodiment has been 'chosen for the purpose of illustration and description, and is shown in the accompanying drawing forming a part of the specfication.

In the drawing:

FIG. 1 is an elevational view of a reservoir partly broken away to better illustrate my invention.

FIIC. 2 is a top plan view of thereservoir shown in FIG. 3 is a perspective view of the passage in comimunication with the inlet and outlet pipes within the from the reservoir through the outlet pipe 21.

An inlet pipe 20 passes through one of the side walls 11 and is directed downwardly towardsV the' bottom of the tank, and a suction or outlet pipe 21 passes upwardly from adjacent the bottom of the tank and through the top wall 16.

In accordance with my novel contribution, I provide an enlarged passage in the form of an inverted channel member 22 secured within the tank to the bottom wall 17. As I have already stated, this. passage or channel member communicates at one end with the inlet pipe 20 and at its other end with the outlet or suction pipe Zl. For'this purpose, the upper surfaceV of the inverted channel member is formed with an opening 24 for receiving the end of the pipe 20, and with a second opening 25 for receiving the end of the pipe 21. I further prefer to provide a series of small openings 26 along the bottom of the side walls of the channel member adjacent the bottom wall 17 of the tank, and below the minimum fluid level in the tank, whereby the interior of the channel member is in limited communication with the interior of the tank or reservoir 10, and I close the ends of the channel member by end walls 27 and 29.

To understand the operation of my present invention, it will be recalled that it is the custom in most industrial trucks to operate the pump continuously while the truck motor is running. Referring to FIG. 4, therefore, it will be seen that the pump P will pump fluid continuously When the rams R are in operation, a by-pass 'or directional valve V willdirect the fluid through the pipe 27 to the rams at which time there will be a surge of fluid out of the reservoir. When the rams R are vented, fluid will leave the rams and return through pipe 20 to the reservoir causing a surge of fluid into the reservoir. When the rams are not in operation, fluid will be pumped from the reservoir through the pipe 21 to the by-pass or directional value V which will return the fluid to the reservoir through the pipes 29 and 20, thereby maintaining the fluid level fairly Constant in the reservoir.

It will be seen that my enlarged passage 22 provides an almost direct communication between the inlet pipe 20 and the outlet pipe 21 within the reservoir. In this manner, the turbulence in the fluid between the inlet and the Outlet pipes within the reservoir is greatly reduced and what little turbulence may exist is confined to the area within the inverted channel member, and does not disturb the fluid in the reservoir. During surges of fluid out of the tank, the openings 26 enable sufiicient fluid to flow from the reservoir through the passage means and into the outlet pipe 21. Similarly, during a surge of fluid into the tank, the same openings permit some of the fluid entering the passage through the pipe 2h to pass into the reservoir. At all times, there is suflicient interchange of fluid between the passage member and the reservoir proper to prevent overheating of the fluid.

From the foregoing description, it will be seen that I have contributed a novel reservoir construction that functions very eifectively in a lifting system of the class described to minimize turbulence and to eliminate cavitation in the hydraulic fluid. At the same time, I provide for necessary Cooling of the fluid and for acceptance within the reservoir of surges of fluid into or out of the reservoir. I believe that the construction and operation of my novel invention will now be fully vappreciated by those persons skilled in the art.

I now claim:

1. A hydraulic circulating system comprising, a hydraulic motor, a pump, a fluid reservoir, a high pressure line connecting the high pressure side of the pump with one side of the hydraulic motor, a low pressure line connecting the low pressure side of the pump with the other side of the hydraulic motor, said lines forming a closed circuit whereby the fluid flowing therethrough is not exposed to air, a portion of said low pressure line extending through said reservoir beneath the surface of the fluid in the reservoir, said portion being in the form of an invertedchannelmember secured to the bottom of the reservoir and having an inlet pipe at one end and an outlet pipe at the other end, said channel member forming a direct passage between said inlet and outlet pipes for the circulation of fluid in said circuit through said reservoir without causing turbulence of fluid in said reservoir outside of said channel member, said channel member having a plurality of small holes through the Wall thereof, said small holes being open at all times to facilitate passage of heat between the fluid flowing through said circuit and the fluid in the reservoir and to permit interflow of fluid between said circuit and the reservoir as necessary to co-rnpensate for changes in the volumetric requirements of the hydraulic system, and said outlet pipe of said channel member being at least as large in cross section as said inlet pipe whereby the fluid circulating through said circuit passes freely through said channel member from said inlet pipe to said outlet pipe and is not forced outwardly through said small holes into said reservoir except When necessary to compensate for a change in the volumetric requirements of the hydraulic system.

2. A hydraulic circulating system comprising, a hydraulic motor, a pump, a fluid reservoir, a high pressure line connecting the high pressure side of the pump with one side of the hydraulic motor, a low pressure line connecting the low pressure side of the pump with the other side of the hydraulic motor, said lines forming a closed circuit whereby the fluid flowing therethrough is not exposed to air, a portion of said low pressure line extending through said reservoir beneath the surface of the fluid in the reservoir, said portion being in the form of a passage member providing a Chamber having spaced inlet and outlet openings, said chamber forming a direct passage between said inlet and outlet openings for the circulation of fluid in said circuit through said reservoir without causing turbulence of fluid in said reservoir outside of said Chamber, said chamber having a plurality of small holes through the wall thereof, said small holes being open at all timesto facilitate passage of heat between the fluid flowing through said circuit and the fluid in the reservoir and to permit interflow of fluid between said circuit and the reservoir as necessary to compensate for changes in the volumetric requirements of the hydraulic system, and said outlet opening of said Chamber being at least as large in cross section as said inlet opening whereby the fluid circulating through said circuit passes freely through said Chamber from said inlet opening to said outlet opening and is not forced outwardly through said small holes into said reservoir except when necessary to compensate for a change in the Volumetric requirements of the hydraulic system.

3. A hydraulic circulating system comprising, a hydraulic motor, a pump, a fluid reservoir, a high pressure line connecting the high pressure side of the pump with one side of the hydraulic motor, a low pressure line connecting the low pressure side of the pump with the other side of the hydraulic motor, a bypass line connecting the high pressure line and the low pressure line for bypassing fluid around the hydraulic motor, valve means for closing said bypassing line, said lines forming closed circuits whereby the fluid flowing therethrough is not exposed to air, a portion of said low pressure line extending through said reservoir beneath the surface of the fluid in the reservoir, said portion being in the form of a passage member providing a chamber having spaced inlet and outlet openings, said chamber forming a direct pas- Sage between said inlet and outlet openings for the circulation of fluid in said circuits through said reservoir without causing turbulence of fluid in said reservoir outside of said Chamber, said Chamber having a plurality of small holes through .the wall thereof, said small holes being open 'at all times to facilit-ate passage of heat betwcnrthe fludfiowing .through said circuits and the fluid in the reservoir and .to permt nterflow of fluid between said circuts and the reservoir as necessary to compensate for changes in the volumetric requirements of the hydraulic system, and said outlet opening of said chamber being at least as large in cross section as said inlet opening Whereby the fluid circulating through said circuits passes freely through said chamber from said inlet opening to said outlet opening and is not forced outwardly through said small holes into said reservoir except iwhen References Cited in the file of this patent necessary to co-mpensate for a change in the volumetric 10 2'767'736 'requirements of the hydraulic system.

UNITED STATES PATENTS Lundskow Oct. 30, 1934 Austin May 20, 1941 Davis Aug. 5, 1941 Tryon Apr. 13, 1943 Miller Aug. 3, 1943 Tibeau Mar. 11, 1952 Lackinger Oct. 23, 1956 

